Tracking-Error Anxiety

Quick definition: Tracking-error anxiety is the obsessive concern that your portfolio's returns do not perfectly match a benchmark (like the S&P 500), leading you to constantly adjust your portfolio to eliminate small deviations.

Key Takeaways

• Tracking error is the deviation of your portfolio returns from a benchmark; small tracking errors over short periods are normal and usually reflect intentional strategic choices.
• Obsessing over tracking error causes you to tinker with your portfolio constantly, incurring costs and taxes that destroy returns far more than the original tracking error.
• Passive investors with intentional strategic tilts (international exposure, bonds, factor tilts) will have tracking error relative to a single-country index, but this is a feature, not a bug.
• Most tracking error is noise; comparing your portfolio to a single benchmark over a single year or quarter is meaningless for long-term investors.
• The goal of a passive investor is not to match any benchmark perfectly, but to maximize risk-adjusted returns within your chosen asset allocation, which often means deviating from common benchmarks.

The Origin of Tracking-Error Anxiety

Tracking-error anxiety originates from a misunderstanding of what "passive investing" means. Some investors interpret passive as "match the S&P 500 as closely as possible." Under this interpretation, if they own a diversified portfolio with 60% U.S. stocks, 20% international stocks, and 20% bonds, and the S&P 500 rises 20% while their portfolio rises 12%, they experience anxiety. "I am underperforming the S&P 500," they think. "There must be something wrong with my portfolio."

This is backwards thinking. Your portfolio is not supposed to match the S&P 500. Your portfolio is supposed to match your chosen asset allocation, which deliberately deviates from the S&P 500. A 60/20/20 portfolio should not match the S&P 500; it should match a 60/20/20 benchmark (60% S&P 500, 20% international stocks, 20% bonds). The fact that it deviates from the S&P 500 is the entire point.

Tracking-error anxiety is further amplified by financial media and comparison culture. Investment websites and apps let you compare your portfolio to the S&P 500 in real-time. Financial media headlines constantly compare portfolios to benchmarks: "Your portfolio beat the S&P 500 by 0.5%! Here is why." Or: "Your portfolio lagged the market this quarter. Should you change your strategy?"

This constant stream of relative-performance data triggers anxiety, which leads to tinkering, which destroys returns.

Why Tracking Error Is Not the Enemy

Tracking error itself is not the enemy. Tracking error is the deviation of your portfolio from a chosen benchmark. For a passive investor with an intentional asset allocation, tracking error is inevitable and healthy.

Consider a 60/40 investor comparing to the S&P 500:

Year 1: S&P 500 returns 25% (a great year for stocks). The 60/40 portfolio returns 18% (60% of the 25% stock gain plus 40% of the 5% bond return). Tracking error: 7% underperformance. Is this a problem? No. The investor expected this tracking error when they chose a 40% bond allocation.

Year 2: S&P 500 falls 20%. The 60/40 portfolio falls 8% (60% of the 20% stock loss minus 40% of the 5% bond loss). Tracking error: 12% outperformance. Is this a benefit? Yes. The bonds provided exactly the cushion the investor expected.

Over a full market cycle (5–7 years), the 60/40 portfolio will have beaten the S&P 500 in down markets and lagged in up markets. The long-term return will be slightly lower than the S&P 500 (because stocks outperform bonds), but the volatility will be much lower. The tracking error relative to the S&P 500 is the price of better risk-adjusted returns and emotional sustainability.

An investor who recognizes that their portfolio is supposed to track a 60/40 benchmark, not the S&P 500, will not experience anxiety. An investor who compares to the S&P 500 will experience constant anxiety and will likely make poor decisions as a result.

The Costs of Chasing Tracking Error

The real damage from tracking-error anxiety is in the attempts to fix it. When an investor becomes anxious about lagging the S&P 500 and decides to "improve" their portfolio by increasing their stock allocation or reducing their international exposure, they incur several costs:

First, there are trading costs. Selling bonds or international stocks to buy more S&P 500 stocks incurs bid-ask spreads and commissions.

Second, there are tax costs. In a taxable account, selling appreciated positions triggers capital gains taxes. The investor pays taxes immediately, reducing after-tax returns. This is an immediate, certain cost to fix a tracking error that is often temporary or illusory.

Third, there is the opportunity cost. The investor changes their allocation based on recent performance (e.g., stocks just had a great year, so I should own more stocks). This is classic performance chasing. The investor buys high and will likely sell low after the next downturn.

Consider a real-world example: An investor starts with a 60/40 portfolio in 2020. Stocks rise sharply; by the end of 2021, their portfolio has drifted to 70/30. Anxious about underperforming the S&P 500, they rebalance back to 60/40 by selling stocks and buying bonds. Trading costs: $2,000. They feel good—they are "getting back on track."

Then in 2022, stocks fall 18% and bonds fall 13%. The investor's 60/40 rebalanced portfolio falls 16.6%, while the S&P 500 falls 18%. The investor was right to own bonds. But they never acknowledge this; they are too focused on the fact that they still lagged the S&P 500.

In 2023, stocks rise 24%. The investor's 60/40 portfolio rises 16%. They panic. "I made a mistake rebalancing into bonds. I should be more aggressive." They sell bonds and buy stocks. Trading costs: $3,000. They move to 70/30. They feel better. They believe they are "getting back on track" toward beating the S&P 500.

Over this three-year period, the investor paid $5,000+ in trading costs and taxes trying to chase the S&P 500, made emotional decisions based on recent performance, and likely ended up with worse risk-adjusted returns than if they had simply stuck to their 60/40 plan. The tracking error anxiety cost them far more than the tracking error itself ever would have.

Comparing to the Right Benchmark

The solution to tracking-error anxiety is to compare your portfolio to the right benchmark. A 60/40 investor should compare to a 60/40 benchmark. An investor with international exposure should compare to a global benchmark. An investor with factor tilts should compare to the tilted benchmark.

This requires some self-awareness. You must decide:

1. What is my target asset allocation? (e.g., 60% U.S. stocks, 20% international stocks, 20% bonds)
2. What is my benchmark for that allocation? (e.g., 60% S&P 500, 20% international index, 20% aggregate bond index)
3. Over what time period am I measuring? (e.g., 3–5 years or longer; not monthly or quarterly)
4. How much tracking error am I willing to tolerate? (e.g., I am comfortable with 1–2% annual deviation from my benchmark due to fund selection or rebalancing)

Once you have answered these questions and written them down, you can measure tracking error against the right benchmark. A 60/40 investor who compares to a 60/40 benchmark will typically find that their tracking error is small (0.5–1.5% annually) and is usually due to reasonable implementation choices (they own a low-cost total market fund instead of owning individual stocks; the fund's expense ratio causes a tiny tracking error).

If the tracking error is small and explained by reasonable choices, there is nothing to worry about. Leave the portfolio alone.

When Tracking Error Matters

Tracking error does matter in one specific context: when you are paying for active management. An active fund manager who charges 1% in fees better deliver 1.5%+ in outperformance through better security selection; otherwise, you are losing money. The tracking error (deviation from the benchmark) is directly related to the value you are getting from active management.

For passive investors, tracking error is nearly irrelevant. You are not paying for active management; you are paying low fees for index exposure. A small tracking error is the price of low costs. A passive investor who obsesses over tracking error should ask themselves: "Am I getting value from the tracking error?" If the answer is no, the tracking error does not matter.

The Noise of Short-Term Performance

A critical insight for managing tracking-error anxiety is understanding that short-term performance is noise. The S&P 500 might outperform your 60/40 portfolio by 5% in a given quarter. This is not meaningful information. It is random variation around the true long-term relationship.

Here is an analogy: Imagine you flip a fair coin 100 times and expect roughly 50 heads and 50 tails. You flip the coin, and the first 10 flips result in 7 heads and 3 tails. Do you worry that the coin is rigged? No. You recognize this as normal variation in a small sample. This is exactly what quarterly or annual tracking error is—noise in a small sample.

Over a full market cycle (5–7 years), the 60/40 portfolio will show what it is truly capable of. In down markets, it will outperform the S&P 500 due to bond ballast. In up markets, it will lag. The multi-year return will show the value (or lack thereof) of the 40% bond allocation.

Investors who obsess over tracking error in monthly or quarterly snapshots are making decisions based on noise. They are like someone constantly checking coin flips and getting anxious if the results deviate from 50/50 in the short term. It is irrational.

The Tyranny of Relevance

One more subtle point: the obsession with tracking error often comes from a desire to "beat the market." A 60/40 investor who lags the S&P 500 feels like they are losing. But "beating the market" is not the goal of passive investing. The goal is to achieve your financial objectives—retire at a certain age, save enough for college, accumulate a certain amount—with appropriate risk.

If your financial objective is to grow $500,000 to $2 million in 30 years with minimal emotional stress, and a 60/40 portfolio does this reliably, then it does not matter if the S&P 500 does better. You have achieved your goal. The benchmark is irrelevant.

A 60/40 portfolio might return 7–8% annually while the S&P 500 returns 10%. Over 30 years, $500,000 grows to roughly $4 million in the 60/40 (7% annually) and $6.5 million in the S&P 500 (10% annually). But perhaps you only need $2 million. In that case, the 60/40 is optimal because it gets you to your goal with less volatility, less stress, and lower likelihood of panic-selling.

Comparing to a benchmark that is not your actual target is the psychological root of tracking-error anxiety. Instead of focusing on your benchmark, focus on your goal. If your portfolio is achieving your goal with acceptable risk, the tracking error is irrelevant. If it is not achieving your goal, then the problem is not tracking error; it is that your asset allocation is wrong for your objectives. Change your allocation intentionally (based on your goals), not reactively (based on recent benchmark performance).

Decision flow

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With these eight common mistakes understood and avoided, you are well positioned to build a passive portfolio that works for your long-term financial success.